This rekenrek abacus features ten rows of two different colored plastic beads that easily slide back and forth on metal rods. The sturdy plastic frame is designed to add desktop stability for student use, and may be used either standing up, or laying flat. An excellent teaching tool for building basic math skills in counting, addition and subtraction. Dimensions 8.27" x 7.87" x 3.54" . This 10-row Rekenrek may look like an ordinary counting frame or abacus, however, it is used in a different way. Rather than counting to ten, this abacus promotes counting by 2's, 5's and 10's. The Rekenrek is a very effective tool in understanding numbers and their relationships. The 10-row Rekenrek is an extended version of the standard 2-row Rekenrek, making it possible to use effective addition and subtraction strategies.